Toughening and functionalization of bioactive ceramic and glass bone scaffolds by biopolymer coatings and infiltration: a review of the last 5 years

Abstract

Inorganic scaffolds with high interconnected porosity based on bioactive glasses and ceramics are prime candidates for applications in bone tissue engineering. These materials however exhibit relatively low fracture strength and high brittleness. A simple and effective approach to improve the toughness is to combine the basic scaffold structure with polymer coatings or through the formation of interpenetrating polymer-bioactive ceramic microstructures. The polymeric phase can additionally serve as a carrier for growth factors and therapeutic drugs, thus adding biological functionalities. The present paper reviews the state-of-the art in the field of polymer coated and infiltrated bioactive inorganic scaffolds. Based on the notable combination of bioactivity, improved mechanical properties and drug or growth factor delivery capability, this scaffold type is a candidate for bone and osteochondral regeneration strategies. Remaining challenges for the improvement of the materials are discussed and opportunities to broaden the application potential of this scaffold type are also highlighted.

Characterisation of Bioglass based foams developed via replication of natural marine sponges

“…7,35 In fact, it is still a challenge to obtain a Bioglass scaffold presenting at the same time good mechanical properties and high porosity. 35 In the present work, the possibility to increase the mechanical behaviour of Bioglass based scaffolds by reducing the total porosity was considered with natural marine sponges, SA and SL, chosen as sacrificial templates for the production of the scaffolds. 25,35 These sponges were characterised by a high interconnected porous structure made by fine fibres.…”

“…In the case of BG-PU, the resulting maximum compressive strength was lower than the average values found in literature (*0.4 MPa). 35 This was probably due to the compressed air used for the removal of the slurry excess after the second and third coating during scaffold preparation. Following this technique, it was easier to maintain an open porosity, but the amount of slurry removed was higher.…”

Finite Element Modeling of the Flexural Mechanical Response of Polymer-Coated Bioactive Glass Scaffolds Composed of Thermally-Bonded Unidirectional Fibers

“…Consequently, once the tensile stress is high enough to initiate a crack, the crack could rapidly propagate through the whole structure, resulting in catastrophic brittle facture. In comparison, the adherent PLA layer in the composite can provide a crack healing mechanism for the outermost glass fibers and a crack bridging mechanism for the composite structure [5][6][7][8][9][10][11][12][13][14]. Failure of the first glass fiber leads to a reduction in the load-bearing capacity of the composite and to load transfer to the neighboring fibers.…”

“…As only the external (circumferential) surface of the glass scaffold is coated with the adherent polymer layer, the surface of the internal pores is available to degrade, release ions and stimulate bone infiltration into the scaffold. An alternative composite system can be formed by coating the entire surface (external surface and internal pore surface) of the thermally-bonded glass-fiber scaffold with a polymer layer [11][12][13] but this could reduce the bioactive potential of the composite scaffold. Another alternative is to coat each glass fiber with a polymer layer prior to assembling them into a 3D scaffold but this would reduce both the mechanical strength and the bioactivity of the composite scaffold when compared to the composite scaffold described in this study.…”

“…As shown for porous bioceramic scaffolds [7][8][9][10], coating the external and internal surface of porous bioactive glass scaffolds with a biodegradable polymer such as polylactic acid (PLA) or polycaprolactone (PCL) can have a strong effect on their mechanical response [6,[11][12][13]. The strength and, in particular, the work of fracture of these polymercoated bioactive glass scaffolds have shown considerable increases over the uncoated scaffolds due to crack bridging and crack healing mechanisms enabled by the polymer coating [6,11].…”